Congestive heart failure (CHF), also called just heart failure, is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with blood or to pump a sufficient amount of blood throughout the body. Heart failure is a common syndrome. By one estimate, heart failure affects 5 million people in the U.S. and 550,000 new cases are diagnosed each year.
One characteristic of heart failure, among others, is autonomic imbalance. Continuously high sympathetic tone can cause increased heart rate, cardiac oxygen consumption, and risks of arrhythmias. Therefore, a common medical therapy for the treatment of heart failure is the administration of beta blockers. Examples of beta-blockers that are indicated for the treatment of heart failure include bisoprolol, carvedilol, and extended-release metoprolol. Beta blockers block the action of certain central nervous system neurotransmitters, such as epinephrine (adrenaline) and norepinephrine (noradrenaline), on the receptors of the sympathetic nervous system that mediate the “fight or flight” response. For example, stimulation of certain receptors by epinephrine induces a positive chronotropic and inotropic effect on the heart and increases cardiac conduction velocity and automaticity. Beta blockers also have an antiarrhythmic effect, which arises from the depression of sinus node function and atrioventricular node conduction, and prolonged atrial refractory periods. Beta blockers inhibit normal epinephrine-mediated sympathetic actions, but have minimal effect on resting patients. That is, they reduce the effect of excitement/physical exertion on heart rate and force of contraction, dilation of blood vessels, opening of bronchi, reduce tremor, and breakdown of glycogen.
However, the use of beta blockers can also result in side effects. The administration of beta blockers is a balance between the effectiveness of the drug in treating the heart disease or other medical condition and the side effects. Because beta blockers tend to depress cardiac activity, a primary side effect is bradycardia or low heart rate. In many cases, the ideal balance point is defined as the dosage of beta blockers that results in a desired resting heart rate, where further increases in dosage would result in a heart rate that is undesirably low. Other side effects of beta blockers include atrioventricular block, which is a delay or interruption in the conduction of electrical signals from the atria to the ventricles, resulting in arrhythmias or bradycardia. Furthermore, beta blockers may also cause hypotension, where the patient's blood pressure is too low, because of the depressive effects of the beta blockers on the patient's cardiac system. Certain other drugs, such as certain antiarrhythmics, can create similar side effects.
The balance between therapy and side effects generally requires that a patient undergoing drug therapy go through a drug titration procedure. Basically, drug titration normally involves first administering a relatively small dosage of a drug, then monitoring the patient's side effects, and subsequently increasing the dosage of the drug until the targeted benefits are achieved or until the patient's side effects meet or exceed a desired threshold. The dosage is increased until the patient's side effects increase to the point that they are judged to warrant no further increase in dosage or that the patient reaches a maximum recommended dosage.
However, improved techniques are needed for drug titration. Current techniques do not necessarily yield optimum results. Furthermore, current drug titration techniques require face-to-face interaction with medical personnel, which consumes resources and is inconvenient for the patient.